444 Stainless Steel (UNS S44400)
Ferritic (Mo-bearing) · ASTM A240/A240M · Density 7.75 g/cm³
Type 444 (UNS S44400, EN 1.4521) is a ferritic stainless steel with 18% chromium and about 2% molybdenum, stabilized with titanium and niobium. Its pitting resistance approaches 316L while remaining immune to chloride stress-corrosion cracking, making it a nickel-free choice for hot-water tanks, solar collectors and heat exchangers.
Chemical Composition (wt%)
| C | Mn | Si | Cr | Mo | Ni | Ti+Nb | N | P | S |
|---|---|---|---|---|---|---|---|---|---|
| ≤0.025 | ≤1.00 | ≤1.00 | 17.5–19.5 | 1.75–2.50 | ≤1.00 | 0.20+4×(C+N)–0.80 | ≤0.035 | ≤0.040 | ≤0.030 |
Single values are maximums unless a range is shown. Balance: Fe. Per ASTM A240/A240M.
Mechanical Properties
| Tensile strength | ≥415 MPa (60 ksi) |
|---|---|
| Yield strength (0.2%) | ≥275 MPa (40 ksi) |
| Elongation (50 mm) | ≥20% |
| Hardness | ≤217 HBW |
Room-temperature minimum values are summarized for annealed flat product under ASTM A240/A240M unless a condition is named in the property label; product form and thickness can change the requirement.
Physical Properties & Structure
| Density | 7.75 g/cm³ |
|---|---|
| Magnetic response | Magnetic because the room-temperature matrix is ferritic. |
| Microstructure | Ferritic (Mo-bearing) |
Corrosion Resistance & Limits
- Ferritic grades resist chloride stress-corrosion cracking better than common austenitic grades, while pitting resistance still depends on chromium, molybdenum and exposure.
- Weld condition, section thickness, crevices, deposits and surface contamination can control service performance; validate the actual fabrication and environment.
Fabrication & Heat Treatment
| Welding | Control heat input, interpass temperature and joint design to limit grain growth and loss of toughness; stabilized grades improve but do not remove these controls. |
|---|---|
| Forming | Formability is useful in sheet gauges but lower than common austenitic grades, especially in heavy sections and severe draws. |
| Machining | Machining is generally straightforward with rigid tooling; avoid smearing, overheating and iron contamination of finished surfaces. |
| Heat treatment | Ferritic grades are not hardened by heat treatment. Annealing can restore ductility, but the temperature and cooling route must follow the product specification. |
Equivalent Grades
The closest international equivalents of 444 Stainless Steel are 1.4521 (X2CrMoTi18-2) in the EN system, SUS444 in the JIS system, 019Cr19Mo2NbTi in the GB system.
These are common corresponding designations, not unconditional substitutes. Verify chemistry, mechanical properties, product standard, delivery condition, dimensions and project approval before changing designation.
| System | Designation |
|---|---|
| UNS | S44400 |
| EN | 1.4521 (X2CrMoTi18-2) |
| JIS | SUS444 |
| GB | 019Cr19Mo2NbTi |
Reference Product Forms & Dimensional Ranges
Common reference product forms for 444 stainless steel: Coil / Strip, Sheet / Plate, Pipe / Tube.
| Finishes | 2B, 2D, BA |
|---|---|
| Sheet / coil thickness | 0.4–3.0 mm |
| Common widths | 1000 / 1219 mm |
Common surface and delivery options: No.1, 2B, BA or mechanically polished finish when supported by the product route; Annealed and pickled, descaled or polished tube finish as specified.
These published ranges are engineering references, not a live-stock or production-capability promise. Confirm the required product form, dimensions, condition, finish and supply route in the quotation.
Typical Applications
- Hot-water tanks and electric water heaters
- Solar thermal collectors
- Plate heat exchangers
- Food and dairy processing surfaces
- Coastal architectural panels
Frequently Asked Questions
How does 444 compare with 316L?
Pitting resistance is comparable — both alloys carry ~2% molybdenum and land near PREN 24–26. 444's advantages: immunity to chloride stress-corrosion cracking (a known 316L failure in hot water) and nickel-free, more stable pricing. 316L counters with easier deep drawing, better weld ductility in heavy sections, and availability in thick plate.
Why is 444 popular for hot water tanks?
Hot chlorinated water is exactly the environment where austenitic 304/316 can crack by chloride SCC. Ferritic 444 cannot fail that way, resists pitting about as well as 316L, and saves the nickel premium — so Japanese and European tank makers standardized on it.
What are 444's limitations?
It is produced mainly in thin gauges (≤3 mm) because heavy ferritic sections lose toughness; welding needs care (matching filler, controlled heat input) and sub-zero impact toughness is limited. For thick structural or cryogenic duty choose an austenitic or duplex grade.
444 Compared With Other Grades
Organizational author: Tsingshan (Shandong) Iron & Steel Co., Ltd..Review method, status and limitations.
Other stainless steel grades:
304304L316316L201321310S4104302205202301309S316Ti347904L409L4204394412507303317L254 SMO440C17-4 PH2304
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